In recent years, to lower silicide resistance in a CMOS process, NiSi or CoSi containing Ni or Co is used as a silicide material. On the other hand, to reduce junction leakage current, an alloy of Ni or Co to which Pt or Pd is added by 5 to 10% is used. When NiPt is used among others, it is expected to achieve improvement in heat resistance and suppression of junction leakage current (see Patent Literatures 1 and 2).
In a silicidization process, after an alloy film is formed on a Si substrate, performing thermal oxidation on the resultant structure causes the alloy to react with Si to form silicide, but a residual portion of the alloy that has not reacted needs to be removed. For example, after NiPt silicide is formed, to remove NiPt that has not reacted, there is a known method using SPM (liquid mixture of sulfuric acid and hydrogen peroxide) (see Patent Literatures 3 and 4).
Further, as a cleaning method for dissolving NiPt with gate metal (such as TiN) etching suppressed, there is a known method using aqua regia (see Patent Literatures 4 and 5).
Moreover, there is a proposed method for performing a treatment using a sulfuric-acid-based oxidant followed by a treatment using a hydrochloric-acid-based oxidant (see Patent Literature 6).